The goals of this proposed study are to adapt ?LifeSkills?- an efficacious and uniquely targeted group- based HIV prevention intervention for young transgender women (YTW) ages 16-29, at risk for HIV transmission or acquisition- to a mobile platform; and once adapted, to conduct a full-scale randomized controlled trial (RCT) to determine its efficacy in decreasing HIV risk behavior. In the U.S., YTW are a key population at high risk of HIV infection, with HIV prevalence estimates in U.S. among urban YTW ranging from 19-22%. Evidence suggests that socioeconomic marginalization, and related psychosocial co- morbidities drive high levels of HIV-related risk YTW, indicating a need for comprehensive HIV prevention programs targeted to their unique circumstances and vulnerabilities. To date there are no evidence-based HIV prevention interventions (EBIs) for YTW listed in the CDC compendium of EBIs; interventions are needed that are widely scalable to the practice environment. We will address this gap via the following study aims: 1) adapting LifeSkills to a mobile web-based platform, including 1a) revising and updating the LifeSkills intervention to include expanded biomedical HIV prevention and treatment modalities (e.g., PrEP and HIV Treatment as Prevention); 1b) adapting the intervention content for mobile deployment with the larger investigative team and YTW at each enrollment site via qualitative focus groups, user-centered design sessions, and usability testing. 2) Pilot testing the adapted mobile intervention to enhance feasibility and acceptability with 40 YTW ages 16-29 at-risk of HIV acquisition or transmission (10 participants/site) and prepare for full implementation. 3) Testing the efficacy of the mobile LifeSkills intervention in comparison to a delayed intervention control group on the primary outcome: number of condomless sex acts (anal and vaginal; 4-month recall) without protection of PrEP/ART; and secondary outcome: acquisition of HIV/STIs (urogenital/anal chlamydia and gonorrhea, syphilis). Furthermore, we will: 3a) examine mediation in HIV risk between intervention groups by the conceptual mediators of the intervention: transgender adaptation/integration, collective self-esteem/empowerment, information, motivation, and behavioral skills. 3b) assess the efficacy of the mobile LifeSkills intervention in comparison to the control condition on outcomes across the HIV prevention and care continuum, including PrEP/HIV care linkage, initiation, and retention, with assessment of effect modification by HIV status (lab-confirmed).